There's a good reason for this. Before release the testers were finding that it wasn't ever viable to build a Sealed Road over Railways. In fact, once you had the IP for it, you could just build rails everywhere, which were cheaper than Sealed Roads, and never bother with roads at all.
To fix this rail now requires a railhead for units to draw supply from it and they cost metal too. Secondly, roads and rails are now way more expensive to build through mountains. Remember that these hexes are literally thousands of kilometres, and the mountainous terrain will take a lot of work to build road or rail through. The amount of effort to build that is likely a lot more than building effort than a formation of soldiers.
Without this, the mountains become trivial to traverse and that's a whole lot of tactical nuance gone from the game. The difficult terrain is supposed to present a significant logistical challenge. Later on, those large IP costs become a lot easier to manage as you're pulling in literally thousands per turn.
< Message edited by KingHalford -- 6/6/2020 1:03:39 AM >